Many semiconductor devices, in particular Light Emitting Diode (LED) devices, utilize semiconductor materials other than silicon. These materials, such as gallium nitride (GaN), gallium arsenide (GaAs), gallium antimonide (GaSb) etc. can be expensive or even not available in a bulk material form. In order to utilize these materials in a cost efficient way, an epitaxial film of the desired semiconductor material is grown on a suitable substrate. However, growing a high quality epitaxial film, with low crystal defect density, is typically facilitated by using a substrate with a closely matching lattice constant.
Presently, sapphire (crystalline aluminum oxide) structures are used as substrates, but they are expensive, costing up to hundreds of dollars for a two inch wafer. It would be economically attractive, and would facilitate circuit integration, to manufacture devices such as LEDs or other semiconductor devices using a less expensive substrate material, such as silicon, to reduce production costs. However, direct epitaxial growth of GaN on a silicon surface tends to produce lower quality epitaxial films with higher defect densities, due to differing lattice constants.